# Operations in the correct order

When you are faced with a mathematical expression that has several operations or parentheses, the solution may be affected by the order in which you tackle the operations. For example, take the expression

$$4\cdot 7-2$$

If we do the multiplication first, we arrive at the following answer:

$$28-2=26$$

If instead we begin by substracting, we get:

$$4\cdot 5= 20$$

In order to avoid confusion and to ensure that everyone always arrives at the same result, mathematicians established a standard order of operations for calculations that involve more than one arithmetic operation. Arithmetic operations should always be carried out in the following order:

- Simplify the expressions inside parentheses ( ), brackets [ ], braces { } and fractions bars.
- Evaluate all powers.
- Do all multiplications and divisions from left to right.
- Do all additions and subtractions from left to right.

**Example**

Suppose you want to figure out how many hours a person works in two days assuming that they work 4 hours before lunch and 3 hours after lunch each day. First, work out how many hours the person works each day:

$$4+3=7$$

and then multiply that by the number of days the person worked:

$$7\cdot 2=14$$

If we were to write this example as one expression, we would need to use parentheses to make sure that people calculate the addition first:

$$\left ( 4+3 \right )\cdot 2=14$$

## Video lesson

Simplify the following expression:

$$2\cdot\left [ \left ( 8-3 \right )+6\cdot \left ( 2 \right ) \right ]-3$$